Questions about the drop-down list ticket

MONETARY_UNIT is the ID of a single drop-down list. I also post my drop-down form program. Please take a look. My initial value is JPY. it should be read-only once the page is opened, but it is useless. If ($ (& quot; # MONETARY_UNIT & quot;). val () = JP drop-down list ticket
MONETARY_UNIT is the ID of a single drop-down list. it does not respond when I write it like this. I also post my drop-down form program. Please take a look. My initial value is JPY. it should be read-only once the page is opened, but it is useless.
If ($ ("# MONETARY_UNIT"). val () = JPY)
{
("# Ss"). addclass ("readonly ")

}


Function monetary_unit ()
{
Echo' JPY';
$ Monetary_unit1 = getmontary_unit (); // Obtain
Foreach ($ monetary_unit1 as $ k => $ v)
{

Echo' '. $ V ["CODE_NAME"].'';

}
}

------ Solution --------------------
If ($ ("# MONETARY_UNIT"). val () = 'jpy ')
{
("# Ss"). addclass ("readonly ")

}